1. Field of the Invention
The present invention relates to an optical element which variably controls the range of exit directions of transmission light, and to a display device, an electronic apparatus, and a lighting device using the same.
2. Description of the Related Art
Display devices such as liquid crystal display devices, for example, are used as information display modules of various kinds of information processing devices such as television sets, personal computer monitors, notebook personal computers, feature phones, smartphones, tablet PCs, PDAs (Personal Digital Assistants) and ATMs (Automatic Teller Machines).
Further, as the displays are becoming large-scaled and multi-purposed, various luminous intensity distribution characteristics are required for the display devices. Particularly, there are demands for restricting the visible range so that others cannot peep at the display and a demand for not emitting light to undesired directions from the viewpoint of information leakage. For dealing with such demands, an optical film capable of restricting the visible range (or the emission range) of the display device has been proposed and has been put into practical use. However, in a case where the display device is viewed from a plurality of directions simultaneously, it is necessary to take out the optical film every time. Therefore, there is an increasing demand for acquiring states of a wide visible range and a narrow visible range arbitrarily without going through a trouble of taking out the optical film.
For meeting such demand, an optical element capable of switching the visible range of the display device between a wide viewing field mode and a narrow viewing field mode has been proposed.
As shown in FIG. 32, this optical element can arbitrarily acquire two states of a wide viewing field mode (see FIG. 32B) with which light 650 is emitted in a wide range and a narrow viewing field mode (see FIG. 32A) with which the light 650 is emitted in a narrow range by disposing an electrophoretic element 140 that is constituted with a dispersion material 142 and electrophoretic particles 141 between light-transmission regions 120 of high aspect ratio arranged independently on a substrate 110 in a planner manner and controlling the dispersion state of the electrophoretic particles 141 in the electrophoretic element 140 with the electric field generated by the voltage from outside.
For example, it is the optical element acquired by: using a transparent substrate; applying, exposing, developing and curing a transparent photosensitive resin layer by applying heat to form the light transmission regions 120; and disposing the electrophoretic element 140 between the light transmission regions.
FIG. 33 is a sectional view showing an optical element 900 of a related art. The optical element 900 includes: a first transparent substrate 110; a transparent conductive film 123 formed on the surface of the transparent substrate 110; a plurality of light transmission regions 120 which are formed on the top face of the transparent conductive film 123 by being isolated from each other; electrophoretic elements 140 disposed between those light transmission regions 120; and a second transparent substrate 115 which is disposed on the light transmission regions 120 and includes another transparent conductive film 125 on the face that is in contact with the light transmission regions 120. The optical element 900 is disclosed in FIG. 8 of U.S. Pat. No. 7,751,667 B2 (Patent Document 1), for example.
However, with the related art disclosed in FIG. 8 of Patent Document 1, both the transparent conductive film 123 and the transparent conductive film 125 are disposed in a planar manner on the element regions of the first transparent substrate 110 and the second transparent substrate 115, so that the electrophoretic particles 141 in the electrophoretic elements 140 migrate simultaneously in a same direction on the transparent conductive film 123 and the transparent conductive film 125. Therefore, operation modes that can be stably achieved are limited to two kinds that are a narrow viewing field mode shown in FIG. 32A and a wide viewing field mode shown in FIG. 32B.
For example, it is possible to acquire a temporal intermediate state through stopping the generation of an electric field by the transparent conductive film 123 and the transparent conductive film 125 in a process of shifting to the wide viewing field mode where the electrophoretic particles 141 in the electrophoretic elements 140 are cohered in the vicinity of the transparent conductive film 123 as shown in FIGS. 42A, 42B from the narrow viewing field mode where the electrophoretic particles 141 in the electrophoretic elements 140 are distributed uniformly as shown in FIGS. 39A, 39B, i.e., in a state where the electrophoretic particles 141 in the electrophoretic elements 140 are distributed in a section from the intermediate position of the transparent conductive film 123 and the transparent conductive film 125 to the transparent conductive film 123 as shown in FIGS. 40A, 40B. However, thereafter, the electrophoretic particles 141 are dispersed spontaneously as shown in FIGS. 41A, 41B, and the mode comes to be shifted to the narrow viewing field mode.
Further, the intermediate state can also be achieved through stopping the generation of an electric field by the transparent conductive film 123 and the transparent conductive film 125 in a process of shifting to the narrow viewing field mode where the electrophoretic particles 141 in the electrophoretic elements 140 are distributed uniformly as shown in FIGS. 39A, 39B from the wide viewing field mode where the electrophoretic particles 141 in the electrophoretic element 140 are cohered in the vicinity of the transparent conductive film 123 as shown in FIGS. 42A, 42B, i.e., in a state where the electrophoretic particles 141 in the electrophoretic elements 140 are distributed in a section from the intermediate position of the transparent conductive film 123 and the transparent conductive film 125 to the transparent conductive film 123 as shown in FIGS. 43A, 43B. However, thereafter, the electrophoretic particles 141 are dispersed spontaneously as shown in FIGS. 44A, 44B, and the mode is also shifted to the narrow viewing field mode.
As described above, the intermediate state between the narrow viewing field mode and the wide viewing field mode can be acquired temporarily in the process of mode shift. However, it is difficult to continuously maintain the photoelectric particles 141 in the intermediate state between the wide viewing field mode and the narrow viewing field mode, so that it is difficult to stably achieve the intermediate mode that is the intermediate state between the narrow viewing field mode and the wide viewing field mode.
It is therefore an exemplary object of the present invention to provide an optical element that is capable of stably achieving, in addition to the narrow viewing field mode and the wide viewing field mode, the intermediate mode that is an intermediate state of the both modes, and to provide a display device, an electronic apparatus, and a lighting device using the same.
In order to achieve the foregoing object, the optical element according to an exemplary aspect of the invention includes: a first transparent substrate; a second transparent substrate provided by opposing to the first transparent substrate; a first conductive pattern and a second conductive pattern disposed on a face of the first transparent substrate opposing to the second transparent substrate; a light transmission region disposed individually between the first conductive pattern and the second conductive pattern to reach a surface of the second transparent substrate from a surface of the first transparent substrate, a pattern thereof transversely crossing an element region; a transparent conductive film disposed on a face of the second transparent substrate opposing to the first transparent substrate; and an electrophoretic element disposed between the neighboring light transmission regions, which is constituted with light-shielding electrophoretic particles of a specific electric charge and a transmissive dispersion material.
As an exemplary advantage according to the invention, the present invention makes it possible to operate the electrophoretic particles for each of the conductive patterns through independently controlling the conductive patterns of a plurality of series that are disposed on the first transparent substrate. Therefore, in addition to the narrow viewing field mode and the wide viewing field mode, it is also possible to stably achieve the intermediate mode exhibiting the intermediate characteristic of the both modes regardless of the time passage.